In conventional disk drives, a controller communicates with a channel circuit, a preamplifier and other elements with a synchronous bus. Clock and data wires of the bus are routed in parallel. Format-control tag signals are time critical and so are not transferred via the bus. The tag signals are commonly generated by sequencers embodied in the controller and transferred on dedicated wires. Mode switching in both the channel circuit and the preamplifier are controlled by the tag signals. As system features proliferate to serve bit-patterned media (i.e., BPM), heat-assisted magnetic recording (i.e., HAMR) and flyheight control, additional precisely-timed tags will be implemented. Such signals will add wires on the channel-to-preamplifier interface. The additional wires consume die pads and cause new traces to be added to an actuator flex-cable.
It would be desirable to implement a tag multiplication via a preamplifier interface.